Apple has started selling contract-free, factory unlocked iPhone-4S models

Apple has started selling contract-free, factory unlocked iPhone-4S in selected stores of U.S. This news was told by 9to5Mac in a post, where they said about the iPhone-4S contract-free and unlocked version.
9to5Mac said,

Although Apple says that they will begin selling unlocked, contract-free iPhone 4S units in the United States in November, we have learned otherwise. Select Apple Stores in the United States have begun selling contract-free versions of the iPhone 4S, which our friend Steven Troughton-Smith was able to both verify and purchase.

Although it was said that Apple will start selling contract-free version in U.S. in the month of November but it has started selling this version.
The contract free version of iPhone-4S can be unlocked simply by connecting the phone to PC with the help of USB cable, and opening iTunes.
You will go through the message "Congratulations, your iPhone has been unlocked" message on the screen and then you can use your iPhone as usual.